Cleaning and disinfection of the root canal system provided by four active supplementary irrigation methods.

This in vitro study evaluated the bacterial reduction provided by the EndoActivator (EA), Easy Clean (EC), passive ultrasonic irrigation (PUI), and XP-Endo Finisher. Eight-four mesial roots of mandibular first molars were instrumented, inoculated with Enterococcus faecalis, and divided into four groups (n. 20). Bacterial reduction in the main canals and dentinal tubules were respectively determined by MTT assays and Live/Dead BackLight technique through confocal laser scanning microscopy (CLSM) at 50, 100, and 150 µm in-depth (n. 10 per group). Statistical analyses were conducted following a significance level of 95% (P < 0.05). A significant statistical difference was just identified between XPF and EC in the main canals. In the dentinal tubules from the main root canals, at 100 and 150 µm in-depths, significant statistical differences were only observed between XPF and EC (P = 0.027) for the former and between XPF and EC (P = 0.011) and XPF and PUI (P = 0.021) for the latter. In the dentinal tubules from the isthmus, at 100 µm in-depth, statistically relevant differences did occur between XPF and EC (P = 0.038) and EC and EA (P = 0.029). At 150 µm in-depth, these differences were only significant by comparing XPF and PUI (P = 0.025) and XPF and EC (P = 0.036). Although no irrigation method could thoroughly disinfect the RCS, bacterial reduction indexes were generally better after using XPF.

Evaluation of changes in root canal length and accuracy of the electronic apex locator during different stages of endodontic treatment and retreatment.

This study evaluated changes in the root canal length (RCL) and the accuracy of the electronic apex locator (EAL) during the different stages of endodontic treatment and retreatment. Fifty-six mesial root canals of mandibular molars were selected. The actual root canal length (AL) of the canals was obtained by inserting a size 15 hand file up to the apical foramen, under magnification. The electronic lengths were obtained at the "APEX" mark of Root ZX II, using an alginate model. Both measurements were performed at three different stages of the initial root canal treatment-unflared, flared, and concluded-and at two stages of retreatment, after achieving patency and repreparation. Data were statistically analyzed and the significance level established was 5%. All stages produced a significant reduction in the AL (p < 0.05). The greatest variation was observed between the unflared-flared stages (0.2 mm) and between concluded-patency stages (0.09 mm), with no difference between them (p > 0.05). The accuracy of Root ZX II was negatively affected after achieving patency, presenting statistically significant difference compared to the other stages (p < 0.05). A significant reduction in the RCL was observed along the different stages of endodontic treatment and retreatment. The EAL was accurate to measure the root canals in most stages, except after achieving patency for endodontic retreatment. Determining and monitoring the RCL is an essential step towards a favorable prognosis, since it reduced along the different stages evaluated. Root ZX II was not accurate for endodontic retreatment.

Morphometric micro-CT study of contralateral mandibular incisors.

OBJECTIVES: This study aimed to determine the degree of similarity and symmetry in the anatomy of contralateral mandibular incisors. Three-dimensional (3D) models of extracted teeth were obtained from microtomography (micro-CT) scans. Qualitative and quantitative assessments of the morphology and comparison of contralateral pairs were made. The null hypothesis was that contralateral mandibular incisors could not be considered identical in simple morphometric measurements. METHODS: Sixty pairs of mandibular incisors were extracted from 30 patients and scanned with micro-CT. Virtual models of the cemento-enamel junction to the root apex were rendered. Parameters such as length, canal width, dentinal thicknesses, tortuosity, centerline length, accessory canals, root canal configurations, and root canal orifice cross-sections were used to compare the teeth. Width and thickness comparisons between paired teeth in the same individual were made by paired t-test (Wilcoxon signed-rank test for variables not normally distributed). An online randomization tool generated randomized pairs (independent of the individual/patient). Subsequently, an unpaired t-test (or Mann-Whitney U test for non-normally distributed parameters) and a correlation analysis were conducted. Canal configurations were classified according to preexisting classification schemes. The number and location of accessory canals and apical foramina were registered and compared. RESULTS: Utilizing advanced imaging techniques and quantitative analyses, our study establishes that contralateral mandibular incisors exhibit a remarkable degree of symmetry in multiple morphological parameters, including length, canal width, and dentinal thicknesses. The apical third showed a high degree of inter-variability for the contralateral pairs. The rigorous statistical analysis of the normalized parameters by Z-score showed no statistically significant differences between the contralateral mandibular incisors. Comparisons between central and lateral teeth revealed differences in root length but no significant disparity in the distribution of accessory canals. Central teeth, on average, were longer, while accessory canals were distributed relatively evenly between central and lateral teeth. CONCLUSIONS: The findings of this study further establish the significant similarities between contralateral mandibular incisors, reinforcing their suitability as a reliable substrate for root canal comparison studies. CLINICAL RELEVANCE: The absence of statistically significant differences between contralateral pairs in normalized parameters underscores their potential as a reliable reference point for root canal comparison studies in clinical dentistry. Furthermore, our findings emphasize the importance of individualized treatment planning, considering the natural symmetry in mandibular incisors to enhance clinical decision-making. This research contributes valuable insights to the field of endodontics, offering a standardized approach to sample selection and enriching the understanding of dental anatomy.

Dynamic Cyclic Fatigue Resistance of Heat-treated Nickel Titanium Instruments in Reciprocating Motion.

OBJECTIVE: To compare the fatigue resistance of different heat-treated reciprocating instruments tested in a dynamic cyclic fatigue model. METHODS: Forty-eight new instruments were inspected under magnification and selected for this study, and then divided as follows (n=12): X1 Blue (MK Life, Porto Alegre, RS, Brazil), Pro-R (MK Life), Reciproc (VDW, Munich, Germany), and Reciproc Blue (VDW). Artificial canals presenting a curvature of 60° angle and 5 mm radius were milled in zirconia. The block containing the artificial canals was mounted in a container filled with water kept at 37°C. A specially designed device was used to perform controlled axial movements while the instruments were activated inside the canals. Time to failure was recorded in seconds, and fragment lengths were measured (mm). Data were analyzed statistically with the significance level set at 5% (One-Way ANOVA and Tukey test). RESULTS: Pro-R and Reciproc Blue instruments presented the highest fatigue resistance, being significantly different from the other tested files (p<0.05). Reciproc presented intermediate results, significantly different X1 Blue (p<0.05). The fractographic analysis showed typical features of cyclic fatigue for all instruments. CONCLUSION: Pro-R and Reciproc Blue instruments are more resistant to dynamic cyclic fatigue than the Reciproc and X1 Blue. (EEJ-2022-10-124).

Effects of CBCT acquisition protocol and additional superimposed computerized optical impressions on the accuracy of root canal length measurements: an ex vivo study.

AIM: The purpose of the present investigation was to evaluate the accuracy of root canal length (RCL) determination according to CBCT acquisition protocol and evaluate the influence of additional superimposed computerized optical impressions. MATERIALS AND METHODS: CBCT scans with low-dose (LD) and high-definition (HD) protocols as well as computerized optical impressions of 30 extracted human molars were acquired. Sicat Endo software (Sicat) was used for CBCT RCL measurements with (LD+, HD+) and without (LD-, HD-) a superimposed optical impression. To evaluate the accuracy, absolute differences between test groups and the actual root canal length (ARCL) were calculated and statistically analyzed using the Wilcoxon rank sum test. RESULTS: Absolute differences between the ARCL and the tested measurement methods varied significantly (P < 0.05). Both higher resolution and additionally superimposed computerized optical impression improved measurement accuracy. Mean differences compared with the ARCL were 0.26 mm (HD+), 0.34 mm (HD-), 0.43 mm (LD+), and 0.66 mm (LD-). 93.4% of all measurements in the HD+ group were within the limits of ± 0.5 mm. CONCLUSION: Both resolution and superimposition of additional computerized optical impressions have a significant influence on RCL measurements using CBCT.

Variations in the morphology of apical constriction affecting electronic readings: An in vitro investigation using 3D-printed tooth models.

We investigated the interference of apical constriction position and diameter on the accuracy of electronic apex locators using 3D-printed tooth models. Single-rooted tooth models with the same length, canal taper and major foramen, but variation in apical constriction position or size, were designed and 3D-printed. A mounting model was custom-made for precise measurement of both marks (0.5 and APEX/0.0) of two electronic apex locators. The electronic measurements of both devices were correlated significantly to the major foramen rather than apical constriction. The mean measurements of the group with 0.45 mm in apical constriction width were significantly shorter than those of the other groups for both marks of the two devices (p < 0.05). The variations in apical constriction position and width negatively affected the precision of the 0.5 mark of the tested devices. The 0.0 or APEX mark was consistently located the major foramen.

Assessment of the Root Canal Similarity in Contralateral Mandibular Incisors.

INTRODUCTION: The purpose of this study was to determine the degree of similarity between contralateral mandibular incisors utilising 3-dimensional (3D) models obtained from micro-computed tomographic (micro-CT) scans of extracted human teeth. The null hypothesis was that contralateral mandibular incisors do not exhibit matching symmetry. METHODS: Sixty pairs (n = 120) of extracted mandibular incisors were obtained from 30 patients and scanned with micro-CT with a voxel size of 15.0 µm. 3D virtual models of the pulpal cavities were rendered. Geometric morphometric deviation analysis was performed after mirroring, automatic alignment, and co-registration of the models of contralateral teeth root mean square (RMS) errors were calculated. The quantitative analysis of the 3D models included 6 different geometric parameters. Data sets were examined with a 2-sample Kolmogorov-Smirnov test. Post hoc retrospective power analysis was performed to find statistical power (α = 0.05). RESULTS: Contralateral pairs had a narrower distribution in deviation than random pairs. Also, contralateral pairs showed a statistically higher similarity coefficient (5 out of 6 geometric parameters) compared to random pairs (P < .001); no difference was found when comparing central to lateral pairs or between Vertucci type I configurations compared to non-type I. RMS errors had significantly lower Contralateral premolars (CPs) values than random pairs (P < .001). CONCLUSIONS: A high degree of similarity was demonstrated for pairing contralateral mandibular incisors using 3D models. The similarity between contralateral central and lateral incisors suggests that when screened and matched, these 4 teeth might be used in endodontic research where similar root canal anatomy is crucial.

Effect of Different Root Canal Drying Protocols on the Bond Strength of Two Bioceramic Sealers.

OBJECTIVES: This study evaluated in vitro the effect of two different drying protocols on the dentin bond strength of two different bioceramic sealers (Sealer Plus BC [SP] and Bio C Sealer [BCS]). Bond strength and failure mode were evaluated according to the sealer, drying protocol, and root canal third. MATERIALS AND METHODS: Sixty extracted human mandibular single-rooted premolars were selected after anatomical standardization. The crowns were sectioned and root canals were prepared. Roots were randomly divided into four groups (n = 15 each). Each group was assigned a combination of one of the evaluated sealers (SP or BCS) and one of the drying protocols: canals dried with paper points (PP) or irrigation with saline followed by aspiration with silicon cannulas (IA). Obturations were performed using a single-cone technique. The teeth were temporized and stored for 7 days (100% humidity, 37°C). Roots were cut to obtain 2 mm thick discs for each third (coronal, middle, and apical). Push-out tests were performed on a universal testing machine, and the bond strength (MPa) of each specimen was calculated by dividing the load (N) by the interface area. Failure type was assessed under ×4 magnification. STATISTICAL ANALYSIS: Data were statistically analyzed with a significance set at 5%. An analysis of variance test followed by the Games-Howell post-hoc test was used to compare the mean values between the groups and the interaction of the variables. RESULTS: The predominant failure type was cohesive, followed by mixed failure and adhesive in all groups. The apical third presented the highest bond strength (p < 0.05) regardless of the group, followed by the middle and coronal thirds. Overall, the SP PP group had the highest mean bond strength (p < 0.01), but the SP sealer was negatively affected by the IA drying protocol in the coronal and middle thirds. The BCS presented similar results within the third stage, regardless of the drying protocol. CONCLUSIONS: Sealer Plus BC had a higher bond strength than Bio C Sealer, but it was negatively affected by the irrigation-aspiration protocol in the coronal and middle thirds. For the apical third, there was no difference between the groups; thus, a similar bond strength was observed regardless of the drying protocol or sealer.

Micro-CT evaluation of four final irrigation protocols on hard-tissue debris removal from mesial roots of mandibular molars containing isthmus.

OBJECTIVES: To evaluate by means of microcomputed tomography (micro-CT), the efficacy of four final irrigation protocols in the removal of hard-tissue debris (HTD) in mesial roots of mandibular molars containing isthmus. MATERIALS AND METHODS: Forty standardized mesial roots of extracted mandibular molars presenting isthmus were selected. The root canals were prepared and randomly divided into 4 groups (n = 10): EA, EndoActivator (Dentsply Sirona); EC, Easy Clean (Easy Dental Equipment, Belo Horizonte, Brazil); XPF, XP-Endo Finisher (FKG Dentaire, La Chaus-de Fonds, Switzerland); and PUI, passive ultrasonic irrigation using Irrisafe tip (Satelec Acteon, Merignac, France). Each final irrigation protocol was performed in two cycles (60 s), using, respectively, 2.5% sodium hypochlorite and 17% EDTA. Micro-CT scans were obtained pre-operatory, post-preparation, and post-irrigation. The percentage of HTD reduction was calculated. Data was analyzed statistically (ANOVA and Kruskal-Wallis, significance set at 5%). RESULTS: The percentage of HTD reduction was greatest for the XPF group (77.92%), followed by EA (62.92%), PUI (47.48%), and EC (32.65%). Statistical differences (p < .05) were found between XPF and EC only. A significant difference (p < .05) was found between XPF and EC in all thirds and between PUI and EC in the middle third. CONCLUSIONS: XPF, EA, and PUI were similarly effective in HTD reduction. However, none of the evaluated protocols was able to completely remove all the debris. CLINICAL RELEVANCE: Final irrigation protocols aim to clean the canal complexities that are not addressed by the shaping procedures. Micro-CT allowed to assess the removal of hard-tissue debris in the isthmus and canals of mandibular molars.

Evaluation of foramen locating accuracy of an endodontic motor integrated with electronic foramen employing optimal glide path kinematics.

OBJECTIVE: This study aimed to evaluate the accuracy of the auto apical function in the maintenance of the apical limit of instrumentation during glide path procedures when associated to OGP kinematics of Tri Auto ZX2, compared to the continuous rotation of the same motor, as well as Root ZX II and VDW Gold. MATERIALS AND METHODS: Forty-eight extracted human mandibular single-rooted premolars were selected. After endodontic access, cervical pre-flaring was performed using size 30, 0.10 taper rotary instruments, and the apical foramen size was standardized to 200 µm. Teeth were randomly divided into four groups (n = 12) according to the device and kinematics. For all the groups, the Auto Apical Stop function (AAS) was set to the 0.0 mark. Glide path instruments size 25, .01 taper were activated inside the canals until the apical limit was reached. Then, the files were fixed with cyanoacrylate to the teeth and decoupled from the equipment. Data were statistically analyzed in GraphPad Prism 6.0 software with the significance set at 5% (Kruskal-Wallis tests). RESULTS: There was no difference in the mean deviation between the groups. No significant difference was found among the groups when the distributions and percentages of differences between the file tip and the apical foramen were compared (P > 0.05). CONCLUSION: The use of auto apical function at the 0.0 mark of all tested devices provided an adequate control of the apical limit during glide path preparation. Foramen locating accuracy of Tri Auto ZX2 in OGP kinematics was similar to those of Tri Auto ZX2, Root ZX II, and VDW Gold in continuous kinematics. CLINICAL RELEVANCE: Clinical strategies in canal negotiation and glide path as OGP motion associated to electronic foramen locators could reduce iatrogenic risk of deviation and file fractures and create an easier initial preparation to facilitate endodontic procedures.

Access Cavity Preparations: Classification and Literature Review of Traditional and Minimally Invasive Endodontic Access Cavity Designs.

INTRODUCTION: Several endodontic access cavity designs have been proposed in the past decade to access the root canal space in a minimally invasive manner. The rationale for this approach was derived from the assumption that preserving more tooth structure during access preparation will improve the tooth's resistance to fracture and its long-term survivability. However, is this assumption valid? Also, can this approach compromise other treatment-related aspects? METHODS: We conducted a literature review using 4 online databases and classified the access cavity designs presented in each article according to our proposed classification. RESULTS: Through the literature search, we identified 49 articles that evaluated the effect of the access cavity design on 11 different treatment parameters. The majority of the studies failed to demonstrate clear benefits of the minimally invasive access designs, whereas others raised concerns regarding the ability to adequately disinfect, fill, and restore teeth with a minimally invasive access cavity design. CONCLUSION: Minimally invasive access cavity designs present more risk than benefit on the outcome of endodontic treatment. Clinicians should reconsider the application of a minimally invasive access cavity for routine endodontics and cautiously apply it in selected cases when the proper armamentarium is available.

Cyclic and Torsional Fatigue Resistance of Seven Rotary Systems.

Introduction: This study aims to evaluate the cyclic and torsional fatigue resistance of seven rotary systems. Methods and Materials: A total of 140 instruments were tested, 20 of each system including Genius (GN) 25/0.04, TruShape (TS) 25/0.06, Logic (LOG) 25/0.06 taper, Vortex Blue (VB) 25/0.06, ProTaper Gold (PTG) 25/0.08, Hyflex CM (HCM) 25/0.06 and Hyflex EDM (EDM) 25/0.08 taper. Cyclic fatigue resistance testing was performed using an artificial stainless steel canal with a curvature (60° angle and 5-mm radius) located at 5 mm from the tip. The files (n=10) rotated until fracture, and time was recorded in seconds. The torsional test was evaluated according to ISO 3630-1. Data were analysed with one-way ANOVA and Tukey's tests (α=5%). The fractured surface of the instruments were assessed using scanning electron microscopy to confirm the type of fracture. Results: The cyclic fatigue resistance value of EDM was significantly higher than those of all tested instruments (P<0.05). LOG showed a higher cyclic fatigue resistance than GN or TS (P<0.05). There was no difference among the other groups (P>0.05). The torsional test showed that PTG 25/0.08 had the highest torsional strength value of all instruments tested followed by VB and EDM (P<0.05). The LOG showed significant difference only with GN (P<0.05). No difference was found among the other groups (P>0.05). In relation to angular deflection, the GN; TS; HCM, and EDM showed significantly higher values until fracture than the other groups (P<0.05). No difference was found among PTG, LOG, and VB (P>0.05). Conclusion: Our in vitro study EDM group had the highest cyclic fatigue resistance among all the tested instruments. For the torsional test, the PTG showed highest torsional strength and lowest angular deflection values.

Management of Root Fenestration Using Buccal Decortication and Guided Tissue Regeneration: A Case Report and 3-dimensional Analysis.

The management of patients with apical fenestration and clinical symptoms has always been limited to apical root resection and placement of the root tip within the bony crypt. This result would often present resolution of clinical symptoms based on a few case studies. In this case report, we present a case in which apical resection alone did not resolve the patient's discomfort; on the contrary, it resulted in further bone loss and persistence of clinical symptoms. A corrective surgery was performed with the use of guided bone regeneration in conjunction with decortication of the cortical plate to induce bleeding. The patient symptoms resolved within a few weeks after the surgery, and the follow-up scan showed apical root coverage. Three-dimensional analysis was performed to compare the bony changes between the 2 surgeries and showed a significant amount of bone gain of around 200 mm3 and a 2-mm linear bone gain opposite the distobuccal root. The case presents a conservative approach to manage root fenestration of the buccal plate without further compromising the root apex.

Accuracy of electronic apical functions of a new integrated motor compared to the visual control of the working length-an ex vivo study.

OBJECTIVES: To evaluate ex vivo the efficacy of the integrated motor Tri Auto ZX2 in controlling the apical extent of preparation compared to conventional visual control (CVC) of the working length (WL). MATERIALS AND METHODS: Eighty standardized mandibular premolars were divided into five groups (n = 16). In the CVC group, instruments were used in continuous rotation (CR) and visual control performed by means of rubber stoppers. For each of the remaining groups, it was assigned a combination of a motion (CR or optimal torque reverse (OTR)), and an apical function (Auto Apical Reverse (AAR) or Optimum Apical Stop (OAS)). Root canals were prepared using the apical functions at 0.5 mark using an alginate model. Difference between the final WL and the actual length post-instrumentation was calculated. Data were analyzed statistically with the significance set at 5% (ANOVA, Tukey HSD). RESULTS: There was no difference in the mean WL among the groups, except between the CR combined to OAS compared to CVC (P > 0.05). Although CVC resulted in two cases beyond the foramen, no significant difference was found among the groups when comparing the distributions of measurements (P > 0.05). CONCLUSIONS: All combinations of motion and apical control functions of Tri Auto ZX2 provided an adequate apical limit ex vivo, similar to the visual control using rubber stoppers. CLINICAL RELEVANCE: TriAuto ZX2 was efficient to control the apical extent of preparation dispensing the need for calibrating the files, regardless of the different settings. This motor might potentially prevent over-instrumentation by continuously monitoring the apical limit.

Endodontic Retreatment Using a Single Instrument from four Nickel-Titanium Systems - A Micro-CT Study.

This study evaluated the efficiency of using a single instrument from three different rotary multi-file systems and compared them with that of a reciprocating single-file for endodontic retreatment by means of micro-CT. Sixty extracted canines were prepared using a size F2 ProTaper Universal file and obturated. After 30 days of storage at 37ºC and 100% humidity, the teeth were randomly divided into four groups (n=15) based on the type of instrument used to retreatment: ProTaper Next (PTN), ProTaper Gold (PTG), TRUShape 3D (TS), and WaveOne (WO). The canals were retreated using only the size 40 instrument from each system according to the manufacturer's recommendations for torque and speed. The time required to remove the filling material was recorded in seconds. The amount of initial and residual filling material and the quantity of dentin removed were assessed by means of micro-CT. Data were statistically analyzed (ANOVA and Kruskal-Wallis) at a 5% significance level. TS instruments required the highest (p<0.05) amount of time (mean, 384.80 ±144.92) compared with the WO (229.67±68.16) and PTG (248.67±64.22) and not so different from PTN instruments (327.67±133.3). No differences in the amount of dentin removed, initial and residual filling volume, and percentages of filling material were observed among the groups. The use of a single rotary instrument from the PTG, TS, and PTN systems was as effective as that of the single-file reciprocating WO system. However, none of the instruments was able to remove the filling materials completely.

Endodontic retreatment using a single instrument from four nickel-titanium systems - a micro-ct study

Abstract This study evaluated the efficiency of using a single instrument from three different rotary multi-file systems and compared them with that of a reciprocating single-file for endodontic retreatment by means of micro-CT. Sixty extracted canines were prepared using a size F2 ProTaper Universal file and obturated. After 30 days of storage at 37ºC and 100% humidity, the teeth were randomly divided into four groups (n=15) based on the type of instrument used to retreatment: ProTaper Next (PTN), ProTaper Gold (PTG), TRUShape 3D (TS), and WaveOne (WO). The canals were retreated using only the size 40 instrument from each system according to the manufacturer's recommendations for torque and speed. The time required to remove the filling material was recorded in seconds. The amount of initial and residual filling material and the quantity of dentin removed were assessed by means of micro-CT. Data were statistically analyzed (ANOVA and Kruskal-Wallis) at a 5% significance level. TS instruments required the highest (p<0.05) amount of time (mean, 384.80 ±144.92) compared with the WO (229.67±68.16) and PTG (248.67±64.22) and not so different from PTN instruments (327.67±133.3). No differences in the amount of dentin removed, initial and residual filling volume, and percentages of filling material were observed among the groups. The use of a single rotary instrument from the PTG, TS, and PTN systems was as effective as that of the single-file reciprocating WO system. However, none of the instruments was able to remove the filling materials completely.

Resumo Este estudo laboratorial avaliou por meio de micro-CT a eficiência do uso de um único instrumento de três sistemas rotatórios em retratamentos endodônticos, comparados a um instrumento único reciprocante. Sessenta caninos extraídos foram preparados usando o sistema ProTaper Universal (F2) e obturados. Após 30 dias de armazenamento a 37 ºC e 100% de umidade, os dentes foram divididos aleatoriamente em quatro grupos (n = 15), de acordo com o instrumento utilizado para remover as obturações endodônticas: ProTaper NEXT (PTN), ProTaper Gold (PTG), TRUShape 3D (TS) e WaveOne (WO). Os canais foram retratados usando apenas o instrumento tamanho 40 de cada sistema, seguindo as recomendações do fabricante para torque e velocidade. O tempo necessário para remover a obturação foi registrado em segundos. A quantidade de material remanescente e o volume de dentina removida foram avaliadas por meio de micro-CT. Análise estatística foi realizada (ANOVA e Kruskal-Wallis), com nível de significância de 5%. O tempo de trabalho no grupo TS foi significativamente maior (p<0.05) (média, 384,80 ± 144,92) comparado a WO (229,67 ± 68,16) e PTG (248,67 ± 64,22), e similar a PTN (327,67 ± 133,3). Não houve diferenças entre os grupos na quantidade de dentina removida e nas porcentagens de material obturador residual. O uso de apenas um instrumento rotatório dos sistemas PTG, TS e PTN foi tão eficaz quanto o do sistema WO reciprocante na remoção do material obturador. No entanto, nenhum dos instrumentos conseguiu remover completamente os materiais obturadores.

Percentage of Gutta-Percha-, Sealer-, and Void-Filled Areas in Oval-Shaped Root Canals Obturated with Different Filling Techniques: A Confocal Laser Scanning Microscopy Study.

OBJECTIVE: This study compared different obturation techniques, analyzing percentage of areas filled with gutta-percha, sealer, and voids (PGFA, PSFA, and PVFA, respectively) in oval-shaped root canals. MATERIALS AND METHODS: A total of 60 extracted human mandibular central incisors were decoronated, instrumented, and irrigated using the same protocol. After drying, the root canal was filled with AH Plus labeled with 0.1% rhodamine B dye using a Lentulo spiral. The filling procedure was performed by dividing the teeth into four groups according to the respective technique: G1, cold lateral condensation; G2, continuous wave of condensation; G3, modified cold lateral condensation using an F3 master cone; and G4, modified continuous wave of condensation using an ISO (International Organization for Standardization) sized 30 gutta-percha cone. Then, slices measuring 1.5 mm in thickness were obtained 3 and 6 mm from the apex and evaluated by confocal laser scanning microscopy to determine PGFA, PSFA, and PVFA. STATISTICAL ANALYSIS: The data were analyzed statistically with analysis of variance and Games-Howell's tests (p = 0.05). RESULTS: The groups showed no significant differences in the apical third (3 mm from the apex). In the middle third (6 mm from the apex), G3 and G1 showed higher PGFA and PVFA, respectively. G3 showed lower PSFA than G2 and G4. Both cold techniques (G1 and G3) promoted lower PSFA than both warm techniques (G2 and G4). CONCLUSIONS: Notwithstanding the limitations of this in vitro study, PGFA, PSFA, and PVFA ranged significantly only in the middle third, as observed by the different filling techniques. Higher PGFA and PVFA values were obtained for G3 and G1, respectively. Both cold techniques promoted lower PSFA than both warm techniques.

Anatomic Two-dimensional and Three-dimensional Models for Cyclic Fatigue Testing of Endodontic Instruments.

Introduction: In this study, new devices were developed and evaluated for cyclic fatigue testing (CTF) of endodontic instruments in two-dimensional (2D) and three-dimensional (3D) replicas of the internal anatomy of a mesial root of a mandibular molar. Methods and Materials: The trajectories of both curved mesial canals of the same root were outlined from computed tomographic scans and exported to a computer assisted drawing (CAD) software. In the CAD program, the canals were virtually enlarged to a size 25/0.06. The CTF devices were then prototyped in stainless steel. The 2D models represented the bucco-lingual (BL) and mesio-distal (MD) views of the canals, while the original trajectory was kept in the 3D model. Vortex Blue 25/0.06 instruments were tested for fatigue in the six canals (n=12). The number of cycles to failure (NCF) and fragment length (mm) were recorded. Data was statistically analyzed (ANOVA and post-hoc Games-Howell test) with the level of significance set at 5%. Results: The mean NCF was significantly different among all the canals (P<0.05). The lifespan of the files was greater in the 2D-BL models, followed by the 2D-MD and 3D. The mean fragment length was also different among the tested models (P<0.05). Conclusions: The tested 2D and 3D representations of the same canal trajectory resulted in significant differences both in the amount of stress (seen from NCF) and localization of the maximum stress (seen from fragment length). Further investigations are required to better understand the effects of different 3D curvatures on the cyclic fatigue of endodontic instruments.

Higher Speed and No Glide Path: A New Protocol to Increase the Efficiency of XP Shaper in Curved Canals-An In Vitro Study.

INTRODUCTION: This in vitro study compared the performance of the XP-endo Shaper (XP; FKG, La Chaux-de-Fonds, Switzerland) in curved canals when used with a higher speed (3000 rpm) without a glide path with the manufacturer's protocol. METHODS: Twenty extracted mandibular molars with separate mesial curved canals were matched to obtain 2 standardized groups (n = 20). For the XP 1000 group, a glide path up to a size 15 hand file was performed followed by rotary instrumentation with the XP shaper at 1000 rpm, following the manufacturer's recommendations. For the canals in the XP 3000 group, the file was rotated at 3000 rpm after only negotiation the canal with a size 8 hand file (patency file). The operating time and the number of strokes taken to reach the working length (WL) and fit a 30/.04 gutta-percha cone to the WL were recorded. The shaping abilities were evaluated by micro-computed tomographic imaging and file deformation by scanning electron microscopy. Data were analyzed using analysis of variance and chi-square tests at a 5% significance level. RESULTS: The XP 3000 group required less time and strokes to reach the WL (P < .05) and resulted in a higher percentage of adequate cone fit (P < .05). No difference was found between groups regarding the micro-CT parameters, except for the taper, which was larger in the XP 3000 group in the apical and middle thirds (P < .05). No difference was found regarding file deformation between the 2 groups. CONCLUSIONS: The suggested protocol for the use of the XP (3000 rpm without a glide path) appears to be more efficient than the manufacturer's recommended protocol to prepare curved canals in vitro.

Microscopic evaluation of the dentinal walls of extracted human teeth following electrochemical dissolution of fragmented nickel-titanium instruments.

Electrochemical dissolution is a method in which fluoridated solution in direct contact with the fractured instrument receives an electrical current that speeds up fragment dissolution. The aim of this study was to assess the integrity of dentinal walls during the electrochemical dissolution of fractured rotary endodontic instruments in extracted human teeth. Forty-five human mandibular incisors subjected to the electrochemical dissolution process using fluoride solution with low NaCl concentration (LC group: NaF 12 g/L + NaCl 1 g/L, pH = 5.0), fluoride solution with saturating NaCl concentration (SC group: NaF 12 g/L + NaCl 180 g/L, pH = 5.0) and distilled water (control group) were evaluated. For each group, 15 incisors were submitted for the scanning electron microscopy (SEM) evaluation. The roots were sectioned longitudinally; each hemisection was analyzed (n = 30), and energy-dispersive spectroscopy (EDS) was performed. The amount of dentinal tubule openings was analyzed by SEM. Statistical analyses were performed. The test solutions did not alter the amount of dentinal tubule openings when compared with the control group. No Ni or Ti was impregnated into the dentinal tubules after electrochemical techniques. The dentinal structure remained unchanged following the electrochemical dissolution method.